Insulator construction



y 0, 1961 M. IRELAND 2,986,594

' INSULATOR CONSTRUCTION Filed May 5, 1958 MRHHHHHH UHHH United States Patent INSULATOR CONSTRUCTION Murray Ireland, Elgin, Ill., assignor to McGraw-Edison Company, Elgin, Ill., a corporation of Delaware Filed May 5, 1958, Ser. No. 733,068

6 Claims. (Cl. 174-138) This invention relates to an improvement in insulators, and more specifically to an insulator which supports electric conductors.

In certain types of electric heaters, an electric insulator is mounted on a support which extends through the center of the insulator and a heating element is supported on the outer periphery of the insulator. Such insulators are generally made of ceramic materials due to the heat resisting and electrical properties thereof. However, such materials tend to fracture rather easily, more particularly, as a result of frequent and extreme temperature changes and mechanical shock, radical cracks develop in the insulator. These cracks extend from the periphery of the insulator to the opening through which the support extends so that the insulator comes apart and falls from the support. When the insulator is gone, the heating element shorts out and the device is usually rendered inoperative.

One of the objects of "the herein disclosed invention is to provide an insulator which supports an electric conductor although the insulator is cracked.

Another object of the present invention is to provide an electric insulator body which supports an electric conductor wherein the insulator body is adapted to receive a holding means which is attached to the insulator body to hold said insulator together should cracks appear in the insulator.

A still further object of the herein disclosed invention is to provide an insulator body and an insulator holding means associated therewith, which are economical to produce and simple to assemble.

Other objects and uses of the invention will become apparent to those skilled in the art upon reading the appended description in light of the drawings, in which:

Fig. 1 is a perspective view of an electric heater including a pair of insulators embodying the present invention;

Fig. 2 is a vertical sectional view taken on line 2--2 of Fig. 1;

Fig. 3 is an exploded perspective view of an insulator embodying the present invention;

Fig. 4 is a longitudinal sectional view taken on line 4-4 of Fig. 2; and

Fig. 5 is a cross sectional view taken on line 5-5 of Fig. 4.

Referring now to the drawings and more particularly to Fig. 1, an electric heater, generally indicated by numeral 10, includes a supporting reflector 12 and an electric heating unit '14.

The supporting reflector 12 consists of a substantially parabolic reflector sheet 16, a lower end plate 18 and an upper end plate 20, which plates hold the sheet in a desired shape. The sheet 16 is formed around the outer periphery of the plates 18 and 20 and fixed thereto.

The aforementioned heating unit 14 is of a conventional type and includes a support rod 22 for mounting the unit within the reflector spaced from sheet 16 sub- 2,986,594 Patented May 30, 1961 stantially at the focus thereof and perpendicular to the end plates. The rod 22 extends through the upper and lower end plates and is supported on upper end plate 20. A washer 24 is positioned on the upper end of the support rod above the plate 20. A pair of crimps 25 is formed in the rod between the terminus of the rod and the washer so that the rod is held by the washer.

As may be seen in Fig. 2, a pair of insulators 26, which constitute part of the heating unit is slidably mounted on the rod respectively proximate the ends thereof. Said insulators are spaced from each other to receive a ribbon-like electric resistance element 27 therebetween as will be hereinafter disclosed. The upper insulator is positioned on the rod proximate the upper end plate 20 and limited in movement in a downward direction by a pair of crimps 28 formed in the rod. The lower insulator is positioned proximate the lower plate 18 and crimps 30 limit the upward movement of the lower insulator. The upper and lower insulators are constructed in an identical manner. Each insulator includes a right circular cylindrical body 48 made of a porcelain, or any other suitable insulating material. As is clearly shown in Fig. 3, each body has a plurality of electric resistance element receiving ears 50 formed integral therewith and radially disposed on the side thereof. Said ears 50 each have a retaining flange 52 integral with the free end thereof, and the resistance element 27 engages the ears 50 between the flange 52 and the body 48. As may be seen in Fig. 4, body 48 has an axial bore 53. An annu-.

is mounted on the body with the openings 58 register-- ing with the opening 53. One of said crowns 56 is posi-- tioned in each of said annular grooves with the rim 60 registering with the respective groove. A tubular bolt 62, having an axial bore 64, extends through the crowns 56 and the body 48. A nut 66 threadedly engages one end of the bolt 62 to hold the crowns 56 in engagement with body 48. As may be seen in Fig. 4, the rod 22 extends through the opening 64 in bolt 62 slidably to support the insulator 26.

The ribbon-like electric resistance element 27 is at-- tached to one ear of the upper insulator and looped back and forth between the upper and lower insulators. The other end of the ribbon is attached to one ear of the lower insulator. The ends of the ribbon 27 are connected to their respective upper and lower terminals 70 and 72, which are mounted on the reflector sheet 16.

The terminals are adapted to be connected to a source of electric current.

The lower end of rod 22 extends through a hole in lower end 18 and through a hole in a U-shaped bracket 36 which is fixed to end 18 by a pair of nuts and bolts 38. The lower insulator has a tension means attached thereto to keep the resistance element taut. Said tension means includes a coil spring 74 attached at one end to the threaded end of the bolt 62 as shown in Fig. 4 and positioned within a slot 76 in the lower end of the rod 22.

When the terminals 70 and 72 are connected to a source of electric power, the current flows through the resistance element 27 to heat the element. As the element 27 is heated, it expands. The expansion of the element is taken up by spring 74 in the tension means, which spring is constantly urging the lower insulator downward. As the element 27 contracts when it cools after the power is cut off, the lower insulator moves 3 upward against the force of the spring 74 to stretch the spring.

The continuous heating and cooling of the insulator body 48 and mechanicalshocks tend to create radial cracks in the body. In the ordinary construction, the body 48 separates into two pieces and the body falls apart allowing the lops of the heating element 27 to short out. Thus, the entire heating unit fails. As any radial cracks develop in body 48, the crowns 56 in grooves 54 provide a holding means to hold the body together even though the cracks may extend from the outer periphery to the opening 53. Thus, the heating element looped over the ears 50 is held in position even though the body 48 is cracked. By use of the instant construction, the life of the insulators is substantially increased; inasmuch as the first appearance of cracks in the porcelain body does not cause a failure of the entire insulator and hence of the entire device.

It is also evident that the present insulator may be made quite economically since the porcelain body with ears integral therewith may be made by any of the conventional methods. The crowns may be stamped out, and the bolt for the connecting means may be manufactured on conventional machines.

While a specific embodiment of the herein disclosed invention has been shown and described, it is obvious that modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.

The invention is claimed as follows:

1. An insulator for use in an electric heating device comprising in combination a one-piece generally cylindrical porcelain body having a plurality of circumfercntially spaced radially extending electric resistance heating element receiving means integral therewith and a generally annnular groove in opposed ends thereof, said body being subjected to changes in temperature and mechanical shock whereby radial cracks may occur therein, a circular generally U-shaped in cross section holding crown disposed in each of said annular grooves, and means engaging said crowns and holding said crowns in engagement with said one-piece body to hold said body together upon the occurrence of said cracks.

2. An insulator for use in an electric device comprising in combination a one-piece generally cylindrical body having a plurality of radially extending electric conductor receiving means attached thereto and a generally annular groove in opposed ends thereof, said body being subject to the development of cracks therein, a circular generally U-shaped in cross section holding crown disposed in each of said annular grooves and means engaging said crowns and holding said crowns in engagement with said one-piece body to hold said body together upon the occurrence of said cracks.

3. An insulator for use in an electric heating device comprising in combination a one-piece generally cylindrical body having a plurality of radially extending elec tric resistance heating element receiving means attached thereto and having a boss at opposed ends thereof, said body being subjected to changes in temperature and me chanical shock whereby radial cracks may occur in said body, and holding means for holding said body together upon the occurrence of said cracks, said holding means comprising generally U-shaped in cross-section holding crowns disposed in surroundingrelation to each of said bosses and means engaging said crowns for holding said crowns in engagement with said one-piece body and clamping said body between said crowns.

4. An electric insulator including a one-piece body portion subject to the development of cracks, said body portion having a plurality of laterally extending electric conductor receiving means attached thereto and a generally annular groove in at least one end thereof, and means for holding said body portion together upon the occurrence of said cracks, said means including a circular generally U-shaped in cross section holding crown disposed in said annular groove in said one end of said body portion and means engaging an opposed end of said body portion for, together with said crown, exerting a clamping force on said body portion.

5. An insulator for use in an electric device comprising, in combination, a one-piece body'having a plurality of electric conductor receiving means attached thereto and having a boss on at least one end thereof, said body being subject to the development of cracks therein, and means for holding said body together upon the occurrence of said cracks, said holding means including a generally U-shaped in cross section holding crown disposed in surrounding relation to said boss in said one end of said body and means engaging an opposed end of said body portion for, together with said crown, exerting a clamping force on said body portion.

6. An electric insulator including a one-piece body portion subject to the development of cracks, said body portion having a plurality of laterally extending electric conductor receiving means attached thereto and a closed groove in at least on end thereof, a generally U-shaped in cross section holding crown disposed in said groove and engaging said body portion at a plurality of opposed points around the periphery of said groove, and means engaging said crown and an end of said body portion opposite said crown for urging said crown into engagement with said body and for exerting a clamping force on said body portion.

References Cited in the file of this patent UNITED STATES PATENTS 588,048 Ashby Aug. 10, 1897 889,956 Nikonow June 9, 1908 1,451,968 Steinberger Apr. 17, 1923 1,628,875 Ehrgott May 17, 1927 1,727,459 Webb Sept. 10, 1929 FOREIGN PATENTS 7 596,965 Germany May 12, 1934 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NOo 2 986 594 May SO 1961 Murray Ireland It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3,, line 3,6 for "annnular" read annular column 4 line 39 for "'on read one =0 Signed and sealed this 24th day of October 19610 SEA L) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC UNITED STATES PATENT OFFICE CERTIFICATE OF CORRCTION Patent N0o 2 986 594 May 30, 1961 Murray Ireland It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent, should read as "corrected below.

Column 3, line 36 for "annnular" read annular g column 4. line 39 for "on" read one =0 Signed and sealed this 24th day of October 1961.,

SEA L) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

